B should be able to win. It depends however if you believe tsukuyomi will end him or not(argument can go both ways), because other than that, he has the superior tools to win. With his sword stance he was pushing back the healthy version of Itachi who could do nothing else than retreating and according to Sasuke, he is even faster in V1, just more linear though. However, it will be enough to put the pressure on Itachi. In this state, the chakra release render amaterasu useless. Totsuka also shouldn't be able to go through the shield even if B was hit because it is kusanagi variant and kusanagi couldn't even scratch it. Underground arms counters Susanoo hard and they can even be controlled from a distance and in close combat, he'd overpower Itachi. Itachi can't also count in a game of endurance either since not only his attacks have drawbacks but B has much greater chakra especially if he lends some from the Biju with the second highest chakra level. He doesn't really need to enter Hachibi mode. However if he does, he should pay more attention in covering himself with his limbs to avoid any amaterasu attempt on the main body(in which case, he lets his limbs take the hit), and run over Itachi with continuous Bijudamas. If meantime, his limbs were affected by black flames, he uses his octopus strategy as a cop out, ending up being a win-win scenario